1. Field of the Invention
The present invention relates to a switch valve structure for switching a fluid machine between a pump mode, to pressurize and discharge a fluid, and a motor mode to convert the fluid pressure at the time of expansion into the kinetic energy and output the mechanical energy.
2. Description of the Related Art
In a conventional vapor compression refrigerator constituting a fluid machine using the Rankine cycle, the compressor of the vapor compression refrigerator can double as an expander to recover energy from the Rankine cycle as disclosed, for example, in Japanese Patent Publication No. 2540738.
In a compressor, the mechanical energy is applied from an external source and a gas such as a gas-phase refrigerant is sucked into a working chamber, after which the volume of the working chamber is reduced to compress and discharge the gas. In an expander, on the other hand, a high-pressure gas is allowed in the working chamber and is expanded by the gas pressure thereby to recover the mechanical energy. To use a compressor as an expander, therefore, the refrigerant flow must be reversed.
In the prior art described above, however, the refrigerant inlet and the refrigerant outlet of the expander (compressor) to recover energy are set on the same side as the refrigerant inlet and the refrigerant outlet of the compressor (expander) to exhibit the refrigeration capacity of the vapor compression refrigerator. Therefore, a single compressor cannot be operated as an expander. In fact, one of the Rankine cycle and the vapor compression refrigerator cannot normally operate.
Specifically, in the compressor, a gas is compressed by displacing a movable member such as a piston or a movable scroll and reducing the volume of the working chamber. Therefore, the discharge port for communication between the working chamber and a high-pressure chamber (discharge chamber) has a check valve to prevent the gas from flowing reversely from the high-pressure chamber to the working chamber.
In the expander, on the other hand, a mechanical output is obtained by allowing a high-pressure gas to flow into the working chamber from the high-pressure chamber and thus displacing a movable member. The mere reversal of the inlet and the outlet of the gas, therefore, cannot supply the high-pressure gas into the working chamber in view of the fact that the check valve poses a stumbling block when the compressor is operated as an expander. The means for reversing the inlet and the outlet of a gas, therefore, cannot operate the compressor as an expander.
In view of this situation, the present inventors earlier conceived a fluid machine (compressor) comprising a high-pressure chamber having a valve mechanism which can be switched to use the fluid machine as a compressor and as an expander (Japanese Patent Application No. 2003-19139).
Specifically, as shown in FIG. 10, a fluid machine 10 includes a pump motor mechanism 100 (similar to the well-known scroll compression mechanism) which is configured of a communication path 106 between a working chamber V and a high-pressure chamber 104 and a spool 107d to open/close the communication path 106. In the case where the pump motor mechanism 100 is used as a compressor, the communication path 106 is closed by the spool 107d, so that the refrigerant flowing in from a low-pressure port 111 is compressed in the working chamber V and discharged from a high-pressure port 110 through a discharge port 105 and a high-pressure chamber 104 (with a check valve 107a opened). In the case where the pump motor mechanism 100 is operated as an expander, on the other hand, the communication path 106 is opened by the spool 107d, so that the vapor refrigerant is allowed to flow in from the high-pressure port 110 (with the check valve 107d closed), and is expanded in the working chamber V through the high-pressure chamber 104 and the communication path 106. Thus, the refrigerant reduced in pressure is allowed to flow out from the low-pressure port 111.
As a result, a fluid machine 10 is obtained which can be used as a compressor and as an expander by reversing the refrigerant flow.
In the valve mechanism described above, however, the spool 107d is slid longitudinally and the communication path 106 open to the flat surface of the mating part is sealed by the flat surface portion at the forward end of the spool 107d. In the case where the perpendicularity between the direction in which the spool 107d slides and the surface to which the communication path 106 is open is low in accuracy, therefore, the sealability is difficult to secure. A low sealability would cause a leak from the communication path 106 closed by the spool 107d, and the fluid compressed by the pump motor mechanism 100 would flow in reverse direction into the working chamber V from the high-pressure chamber 104. This fluid would require compression again, resulting in the power loss of the pump motor mechanism 100.